val vertex2string : Geometry.vector -> float -> string
val face2string : int -> string
val face2stringi : int -> int -> int -> string
val openObj : string -> out_channel
val closeObj : out_channel -> unit
val write_triangle : out_channel -> Geometry.triangle -> int -> float -> unit
val write_point : out_channel -> Geometry.vector -> float -> unit
val write_face : out_channel -> Geometry.trianglei -> unit
